Ion Conduction, Morphology, and Network Formation in a Double-Helix Ionic Polymer Composite Electrolyte

Collective intermolecular interactions can give rise to surprising material properties.  I will describe a distinct class of polymeric ion conductors that we term molecular ionic composites (MICs).  MICs are an integrated combination of ionic fluids with the sulfonated Kevlar®-like polymer “PBDT.” PBDT forms a double helix that provides a rigidity persistence length of ~ 1 micrometer along the rod axis (20X that of DNA), and thus represents a new 1D material building block.  MICs appear to consist of a collective electrostatic network that enables their transport and mechanical properties.  MICs simultaneously possess high mechanical stiffness (E’ up to ~ 1 GPa) and yet liquid-like motions of ions inside (conductivity up to 8 mS/cm), and stability to 300°C.  MICs show promise for enabling, e.g., high density and safe Li and Na batteries, as well as a host of other electrochemical and molecular separations devices.

To characterize these materials, we employ a range of NMR methods that include spectroscopy and diffusometry, and we combine these with X-ray scattering, molecular dynamics simulations, electrochemistry, and microscopy.  I will discuss the phenomena that give rise to MIC properties, and will provide insights into the interplay between multi-scale structure and ion transport in these nanoconfined systems.